Save custom object in .yml

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Hi, does anyone know how to save a custom object in .yml using FileStorage ?

According to the online document: http://docs.opencv.org/3.0-rc1/dd/d74...

I add the following snippet in my custom class ColorSample:

void ColorSample::read(const FileNode& node) {
mat = (Mat)node["mat"]; // Error: no matching function for call to cv::Mat::Mat(cv::FileNode)
loc = (Point)node["loc"]; // Error: no matching function for call to cv::Point_<int>::Point_(cv::FileNode)
color = (Scalar)node["color"];
}

Does anyone know how to solve the first two lines in ColorSample::read() ? Thanks